Query to select and combine uppermost and lowermost value from tables - sql

Question

We have the following tables on our SQL Server 2012.
Table A (data):
ID, Description
---------------
1 , Bla 1
2 , Bla 2
3 , Bla 3
Table P (data):
ID, ParentID, Name
------------------
1 , NULL , AAA
2 , 3 , CCC
3 , 1 , XXX
Table X (foreign keys A_ID to A.ID and P_ID to P.ID):
ID, A_ID, P_ID
--------------
1 , 1 , 1
2 , 1 , 2
3 , 2 , 1
4 , 2 , 2
5 , 2 , 3
6 , 3 , 1
Question:
We need a query something like:
SELECT ...
WHERE A_ID = 1
which should return this result:
ID, Name, Subname
-----------------
2 , AAA , CCC
Name needs to contain the upper most Name from Table P, i.e. the one that has no ParentID.
Subname needs to contain the bottom most Name from the Table P for which the ID still exists in Table X.
ID needs to contain the ID from Table X where P_ID is the ID of the bottom most child.
Another example:
SELECT ...
WHERE A_ID = 2
should return this result:
ID, Name, Subname
-----------------
4 , AAA , CCC
And
SELECT ...
WHERE A_ID = 3
should return this result:
ID, Name, Subname
-----------------
6 , AAA , NULL
We've tried various queries, but some work only for 'where A_ID = 1' and not for 'where A_ID = 2'. In order to select the lowest level child from P, we've looked at the 'How to select lowest level in hierarchy form table post' which probably comes in handy for the query we're looking for.
A single query would be nice, but we will accept a stored procedure as well.
Thanks in advance!
Information
The ID columns in all tables are primary keys
The ID columns in any given table can be changed to any other value in the sample data, while taking into account the primary and foreign key constraints. (E.g. changing P.ID '2' to '4' also results in the change of X.P_ID's '2' to '4'.) This is to show that ID's are not necessarily in order.
Values in the column P.Name can be any non-null value.
Table P can have multiple rows with ParentId set to null.
Sample Data
Taken from #NEER
DECLARE #A TABLE (ID INT, DESCRIPTION NVARCHAR(10))
INSERT INTO #A
VALUES
(1 , 'Bla 1'),
(2 , 'Bla 2'),
(3 , 'Bla 3')
DECLARE #P TABLE (ID INT, ParentID INT, Name NVARCHAR(10))
INSERT INTO #P
VALUES
(1 , NULL , 'AAA'),
(2 , 3 , 'CCC'),
(3 , 1 , 'XXX')
DECLARE #X TABLE (ID INT,A_ID INT,P_ID INT)
INSERT INTO #X
VALUES
(1 , 1 , 1),
(2 , 1 , 2),
(3 , 2 , 1),
(4 , 2 , 2),
(5 , 2 , 3),
(6 , 3 , 1)

Answer 1

Try with the below query. I think Table A is not required for getting the desired result.
SELECT TOP 1 First_VALUE(x.ID) OVER(ORDER BY x.ID desc) ID
,First_VALUE(Name) OVER(ORDER BY p.ID) Name
,CASE WHEN First_VALUE(Name) OVER(ORDER BY p.ID) = First_VALUE(Name) OVER(ORDER BY p.ID desc) THEN NULL
ELSE First_VALUE(Name) OVER(ORDER BY p.ID desc) END SubName
FROM [table P] p
JOIN [table X] x
ON p.ID=x.[P_ID]
WHERE x.[A_ID]=3

Answer 2

Try following query
DECLARE #TableA AS TABLE (ID INT,Des NVARCHAR(MAX));
Insert Into #TableA VALUES(1,'Bal 1'); Insert Into #TableA VALUES(2,'Bal 2'); Insert Into #TableA VALUES(3,'Bal 3');
DECLARE #TableP AS TABLE (ID INT,ParentID INT,Name NVARCHAR(MAX));
Insert Into #TableP VALUES(1,Null,'AAA'); Insert Into #TableP VALUES(2,1,'BBB'); Insert Into #TableP VALUES(3,2,'CCC');
DECLARE #TableX AS TABLE (ID INT,A_ID INT,P_ID INT);
Insert Into #TableX Values(1,1,1); Insert Into #TableX Values(2,1,2); Insert Into #TableX Values(3,2,1); Insert Into #TableX Values(4,2,3); Insert Into #TableX Values(5,3,1);
Select Top 1 X.ID,(Select top 1 Name from #TableP Where ParentID is null) Name,P.Name as SubName
from #TableX as X
Inner Join #TableP as P On P.ID=x.P_ID And P.ParentID IS Not Null
Where A_ID=1
Order by X.ID Desc
Select Top 1 X.ID,(Select top 1 Name from #TableP Where ParentID is null) Name,P.Name as SubName
from #TableX as X
Left Join #TableP as P On P.ID=x.P_ID And P.ParentID IS Not Null
Where A_ID=2
Order by X.ID Desc
Select Top 1 X.ID,(Select top 1 Name from #TableP Where ParentID is null) Name,P.Name as SubName
from #TableX as X
Left Join #TableP as P On P.ID=x.P_ID And P.ParentID IS Not Null
Where A_ID=3
Order by X.ID Desc

Answer 3

You can try the following
with report as (
select max(x.ID) as ID, min(x.P_ID) as MinP, max(x.P_ID) as MaxP
from X x
where x.A_ID = 1 -- <-- here you can change the value
)
select r.ID,
mn.Name as Name,
case when r.MinP = r.MaxP then null else mx.Name end as Subname
from report r
inner join P mn on mn.ID = r.MinP
inner join P mx on mx.ID = r.MaxP
Hope this will help you

Answer 4

Try it with a GROUP BY:
SELECT x.a_id, max(x.id) AS id, min(p.name) AS name,
CASE WHEN max(p.name) = min(p.name) THEN NULL
ELSE max(p.name) END AS subname
FROM p INNER JOIN x
ON p.id = x.p_id
GROUP BY x.a_id
HAVING x.a_id = 1
Still works with your updated sample data. Tested here: http://sqlfiddle.com/#!9/99597f/1

Answer 5

You can use Recursive CTE as the below:
DECLARE #A TABLE (ID INT, DESCRIPTION NVARCHAR(10))
INSERT INTO #A
VALUES
(1 , 'Bla 1'),
(2 , 'Bla 2'),
(3 , 'Bla 3')
DECLARE #P TABLE (ID INT, ParentID INT, Name NVARCHAR(10))
INSERT INTO #P
VALUES
(1 , NULL , 'AAA'),
(2 , 3 , 'CCC'),
(3 , 1 , 'XXX')
DECLARE #X TABLE (ID INT,A_ID INT,P_ID INT)
INSERT INTO #X
VALUES
(1 , 1 , 1),
(2 , 1 , 2),
(3 , 2 , 1),
(4 , 2 , 2),
(5 , 2 , 3),
(6 , 3 , 1)
DECLARE #A_ID INT = 2
;WITH Parents
AS
(
SELECT
P.ID, P.ParentID, P.Name
FROM #P P WHERE P.ParentID IS NULL
UNION ALL
SELECT
P.ID, Parent.ID, Parent.Name
FROM
#P P INNER JOIN
Parents Parent ON P.ParentID = Parent.ID
), Temp
AS
(
SELECT
X.ID,
Parent.Name Name,
IIF(P.ParentID IS NULL, NULL, P.Name) SubName
FROM
#A A INNER JOIN
#X X ON X.A_ID = A.ID INNER JOIN
#P P ON X.P_ID = P.ID LEFT JOIN
Parents Parent ON P.ParentID = Parent.ID OR (P.ParentID IS NULL AND P.ID = Parent.ID)
WHERE
A.ID = #A_ID
), MainTable
AS
(
SELECT
Temp.ID ,
Temp.Name ,
Temp.SubName,
COUNT(Temp.ID) OVER (PARTITION BY Temp.Name ORDER BY (SELECT NULL)) CountOfRowByParent
FROM
Temp
)
SELECT
MainTable.ID ,
MainTable.Name ,
MainTable.SubName
FROM
MainTable
WHERE
(
MainTable.CountOfRowByParent > 1 AND
MainTable.SubName IS NOT NULL
) OR
MainTable.CountOfRowByParent = 1
Result for 2:
ID Name SubName
4 AAA CCC
5 AAA XXX